Sending game invites using Multiplayer Manager

std::string customActivationContext = "{ \"customGameData\": 1 }"; // This string can be anything your game sends across to the invited player's game.

HRESULT hr = XblMultiplayerManagerLobbySessionInviteFriends(xuserHandle, nullptr, customActivationContext.c_str());

size_t xuidsCount = 1;
uint64_t xuids[1] = {};
xuids[0] = 1234567891234567;
HRESULT hr = XblMultiplayerManagerLobbySessionInviteUsers(
    xblUserHandle, 
    xuids, 
    xuidsCount, 
    nullptr,    // ContextStringId 
    nullptr     // CustomActivationContext
);